試題詳解

39. Consider the following 4 objects rolling down the same slope from the same height without slipping: a solid copper ball of radius R, a hollow copper ball of radius R, a solid silver ball of radius R, and a hollow silver ball of radius R. Note that the mass density of silver is greater than that of copper. Assume that all the objects have the same initial center-of-mass velocity and travel down the slope. The moment of inertia for a solid sphere and a hollow sphere is  and , respectively. Which of the following statements is true?
(A)The silver solid sphere, when reach bottom of the slope, is the fastest.
(B)The silver hollow sphere, when reach bottom of the slope, is the fastest.
(C)The copper hollow sphere, when reach bottom of the slope, is the fastest.
(D) All solid spheres, when reach bottom of the slope, are the fastest and have the same speed.
(E)All hollow spheres, when reach bottom of the slope, are the fastest and have the same speed.